How I Didn't Do Well In Physical Education?

My high school gym teacher wanted his students to wear gym uniform during class. I didn't wear gym clothes all the time or most of the time because I felt embarrassed about myself. Because I didn't wear my gym uniform most of the time or all the time in Physical Education. I got a bad grade of D or lower. I started to wear my gym clothes a few times so when report cards came in I got a C. I realize now that choosing to wear your gym uniform either most of the time or all the time will help me get a better grade but it was too late for me.